It is known in the art to improve certain chemical reaction kinetics by increasing the pressure and temperature at which the reaction is conducted. One method of achieving the desired conditions has been to utilize a deep well hydraulic column or gravity pressure reactor vessel, such as disclosed in U.S. Pat. Nos. 3,853,759, 4,272,383 and 4,792,408. Such reactors include a plurality of concentric or nested columns, such that an inner column and an outer column have opposing surfaces. Reactants are introduced into the areas between the columns, and a downflow is created to carry the reactants to the bottom of the reactor vessel where the reaction takes place with the resulting products of the reaction traveling upwardly between other columns.
It is known that organic growths such as algae build up on the column surfaces, especially when raw water such as river water is introduced into and heated in these reactors. Further, when water or other reactants are heated, minerals such as calcium sulphate often become deposited on the surfaces of the columns. Other reactants, contaminants and by-products such as oil and the like may also be deposited on the column surfaces.
These deposits will eventually restrict the flow between the columns, it having been found that once the deposits have built up to as little as one eighth of an inch, they must be cleaned off in order to maintain the reactor in proper operating condition. Heretofore, the cleaning of concentric column reactors has involved pre-treating the deposits with an alkali conditioner, washing the columns with an acid solution and then purging the system. Nitric acid is commonly used, which is known to be unstable and dangerous.
The reactor must be completely shut down and cooled before such cleaning takes place. It has been found that when heating waste bearing waters with normal mineral content, cleaning is needed approximately once every ten days. The cleaning process may take as long as an entire day, which means that the reactor effectively loses ten percent of its operating capacity.
Therefore, a need exists for an improvement in concentric column cleaning in general, and specifically for cleaning gravity pressure reactor vessels having concentric hydraulic columns.